Intraocular lenses (IOLs) are implanted in patients' eyes either to replace a patient's lens or, in the case of a phakic IOL, to complement the patient's lens. For example, the IOL may be implanted in place of the patient's lens during cataract surgery. Alternatively, a phakic IOL may be implanted in a patient's eye to augment the optical power of the patient's own lens.
Some conventional IOLs are single focal length IOLs, while others are multifocal IOLs. Single focal length IOLs have a single focal length or single power. Objects at the focal length from the eye/IOL are in focus, while objects nearer or further away may be out of focus. Although objects are in perfect focus only at the focal length, objects within the depth of field (within a particular distance of the focal length) still acceptably in focus for the patient to consider the objects in focus. Multifocal IOLs, on the other hand, have at least two focal lengths. For example, a bifocal IOL has two focal lengths for improving focus in two ranges: a far focus corresponding to a larger focal length and a near focus corresponding to a smaller focal length. Trifocal IOLs have three focuses: a far focus, a near focus and an intermediate focus corresponding to a focal length between that of the near and far focuses. Multifocal IOLs may improve the patient's ability to focus on distant and nearby objects. Such IOLs may be of particular use for patients suffering from presbyopia, which adversely affects the eye's ability to focus on both far and near objects.
Although multifocal lenses may be used to address conditions such as presbyopia, there are drawbacks. A patient may experience increased incidences of visual disturbances. Visual disturbances are unwanted side effects, such as ghost images, halos, glare or hazy vision, due to the multiple focuses of multifocal IOLs. For example, because of the different focal lengths, multiple images may be formed for a single object. One image due to the focal length in the appropriate distance range is in focus, while the ghost image due to the focal length of the other distance range is out of focus. Such ghost images are undesirable. As a result, the intensity and sharpness of ghost images are desired to be decreased. Similarly, it may be desirable to mitigate other visual disturbances for multi-focal lenses.
Accordingly, what is needed is a system and method for addressing visual disturbances in multifocal IOLs.